Aluminum (Al) sheets of varying thickness are often used in x-ray imaging in x-ray beam hardening or measuring the x-ray beam quality. The total atomic cross section of photons in Al at the energy of 25 keV is 82.24 b/atom. Calculate the linear attenuation coefficient of Al in units of mm- at the 25 keV photon energy. Calculate the mass attenuation coefficient of Al in units of cm/g at the 25 keV photon energy. (a) (b)